Varroa destructor

Varroa destructor (Varroa mite) is an external parasitic mite that attacks and feeds on the honey bees Apis cerana and Apis mellifera. The disease caused by the mites is called varroosis. The Varroa mite can only reproduce in a honey bee colony. It attaches to the body of the bee and weakens the bee by sucking fat bodies . They are a vector for at least 5 debilitating bee viruses including RNA viruses such as the deformed wing virus (DWV). A significant mite infestation will lead to the death of a honey bee colony, usually in the late autumn through early spring. The Varroa mite is the parasite with possibly the most pronounced economic impact on the beekeeping industry. Varroa is considered to be one of multiple stress factors contributing to the higher levels of bee losses around the world. The adult female mite is reddish-brown in color, while the male is white. Varroa mites are flat, having a button shape. They are 1–1.8 mm long, 1.5–2 mm wide and have eight legs. Mites reproduce on a 10-day cycle. The female mite enters a honey bee brood cell. As soon as the cell is capped, the Varroa mite lays eggs on the larva. The young mites, typically several females and one male, hatch in about the same time as the young bee develops and leave the cell with the host. When the young bee emerges from the cell after pupation, the Varroa mites also leave and spread to other bees and larvae. The mite preferentially infests drone cells, allowing the mite to reproduce one more time with the extra three days it takes a drone to emerge vs a worker bee. This can cause genetic defects such as useless wings or viruses and fungi in the bee. Adult mites suck on the fat body of both adult bees and bee larva for sustenance. As the fat body is crucial for many bodily functions such as hormone and energy regulation, immunity, and pesticide detoxification, the bee is left in a severely weakened state. Adult mites live and feed under the abdominal plates of adult bees primarily on the underside of the metasoma region on the left side of the bee. Adult mites are more often identified as present in the hive when on top of the adult bee on the mesosoma region, however research suggests that mites in this location are not feeding but rather attempting to transfer to another bee. Open wounds left by the feeding become vectors for diseases and viruses. They are a vector for at least 5 and possibly up to 18 debilitating bee viruses including RNA viruses such as the deformed wing virus (DWV). With the exception of some resistance in the Russian strains and bees that have Varroa Sensitive Hygiene (VSH) (about 10% of colonies naturally have it), the European Apis mellifera bees are almost completely defenseless against these parasites. (Russian honey bees are one-third to one-half less susceptible to mite reproduction). The model for the population dynamics is exponential growth when bee brood are available, and exponential decline when no brood is available. In 12 weeks, the number of mites in a western honey bee hive can multiply by (roughly) 12. High mite populations in the autumn can cause a crisis when drone rearing ceases and the mites switch to worker larvae, causing a quick population crash and often hive death. Once infected with a Varroa destructor mite, there are two ways for which the honey bee may be damaged. Firstly, the mite’s consumption of the fat body weakens both the adult bee and the larva, in particular it significantly decreases the weight of both the hatching and adult bee. Additionally infected adult worker bees have a lower lifespan than ordinary worker bees, they furthermore tend to be absent from the colony far more than ordinary bees which could be due to their reduced ability to navigate or regulate their energy for flight. Secondly, the mites are vectors of various viruses, in particular the Deformed wing virus